Brake Bias & Proportioning - Shop Car Update
 

We've been working on the brakes and fuel system for the last couple days. We should be able to pressurize the system this week.

We added a Tilton proportioning valve along with the in car bias bar adjustment for true in cockpit brake tuning capability. We will have front and rear brake pressure sensors logged along with all four wheel speed sensors so we should be able to get a really good idea of the braking capability and setup that works on these cars.

Just the line from the rear master to the prop valve and the two pressure sensors and we can start bleeding the system.
https://scontent-atl3-1.xx.fbcdn.net...3e&oe=56C5093C

Tilton proportioning valve in place. We ran a new single rear brake line from here to a split at the rear subframe for the two rear calipers.
https://scontent-atl3-1.xx.fbcdn.net...37&oe=5688A8E0

From the bottom
https://scontent-atl3-1.xx.fbcdn.net...c3&oe=5686B3B4

We've had a lot of questions about why we have a dual master cylinder bias bar setup and a proportioning valve. For those that haven't used both or looked into it the dual master cylinder setup allows a true adjustment of front to rear brake force bias. A proportioning valve actually limits brake pressure to a lower rate of pressure increase creating a "knee point" in the rear brake force in relation to pedal force and front brake pressure. Below is an example of what adjusting the proportioning valve will do to the rear brake pressure.
http://img.photobucket.com/albums/v6...ValveChart.jpg

Quick pic of the mounted bias bar adjustment mechanism, it looks like odd placement but where I'm sitting (as low and far back as possible) it's perfect placement for my left hand.
https://scontent-atl3-1.xx.fbcdn.net...aa&oe=568FFB67

This probably sounds crazy but we switched everything over to standard fittings even on the lines we reused just to save weight. They are drastically smaller tube nuts and "tee" fittings in general. Race cars don't get light 50lbs at a time. They get light an ounce at a time over and over again.

Standard tee fitting weight:
https://scontent-atl3-1.xx.fbcdn.net...f3&oe=56CED139

The OEM and equivalent metric tee... sure it's only 73 grams but it's also 74% when you add up opportunities like this all over the car it makes a big difference.
https://scontent-atl3-1.xx.fbcdn.net...ee&oe=568F04B1

Awesome, do you guys have any more shots of your cage? looks very clean from what I can see in the background of photos

Looks great! What are the plans for this car? What series?

- Andrew

There are a few more posted a couple threads down. Thanks!

Just Time Attack mostlty. I don't have time or budget for a full series. I'll run as many WTAC races as I can though.

we did the same thing on our car, did you build the mecanism or did you buy an off the shelf kit like we did?


http://www.ft86club.com/forums/showt...highlight=puma

We built ours, I didn't even know something like that was readily available. We're planning to offer ours as a kit for a few cars.

Just out of curiosity on that setup how are they keeping the shaft from the brake pedal to the bias bar centered?

not sure i understand the question, the bias bar is built within the box it came with, it is centered with the bar by default, you only need a link from the link to the pivot which is what we did. You could be a little cross side with the pedal, the bias bar would still move in the correct direction.


Although i may have the question wrong. It is basically a universal kit, we had to make it fit, yours will probably fit better from the shelf.

You can check out compbrake for additionnal pictures under "pedal boxes" if you want to get more idea for your product.


I love how you can see where you are at on the bar with the thing you installed on the adjustment knob, we don't really have a way of knowing where the bias is other than poping the hood and checking the distance on each side

Yeah this is my first time using that style bias adjuster, it has a nice smooth action and locks into place at each "notch" in the scale. It's just an Allstar Performance part available from Summit or probably anywhere else if you're interested. I always hated not knowing where you were in the adjustment as well...

http://www.summitracing.com/parts/aa...2078/overview/

A little to late to get any ideas at this point. I was just interested and surprised to see something that functions virtually the same but is actually fundamentally pretty different in design. Obviously they had to make it a little more extravagant to make it universal but even aside from that their push rod system is totally different.

thanks for link, we will look into that.

Nice setup, thinking about doing the same thing in the near future.